Add generic envelope filter and re-implement fade in/out using it

libs/audio/include/psemek/audio/effect/envelope.hpp

@@ -0,0 +1,67 @@
+#include <psemek/audio/stream.hpp>
+#include <psemek/audio/duration.hpp>
+
+namespace psemek::audio
+{
+
+	namespace
+	{
+
+		template <typename EnvelopeFn>
+		struct envelope_impl
+			: stream
+		{
+			envelope_impl(stream_ptr stream, EnvelopeFn envelope_fn, std::optional<duration> truncate)
+				: stream_(std::move(stream))
+				, envelope_fn_(std::move(envelope_fn))
+				, remaining_(truncate ? std::optional{truncate->samples()} : std::nullopt)
+				, total_length_(truncate ? stream_->played() + *remaining_ : stream_->length())
+			{}
+
+			std::optional<std::size_t> length() const override
+			{
+				return total_length_;
+			}
+
+			std::size_t read(util::span<float> samples) override
+			{
+				std::size_t const max_count = remaining_ ? std::min(*remaining_, samples.size()) : samples.size();
+
+				auto const count = stream_->read(samples.prefix(max_count));
+				if (remaining_)
+					*remaining_ -= count;
+
+				auto out = samples.data();
+				for (std::size_t i = 0; i < count; i += 2)
+				{
+					float gain = envelope_fn_(played_);
+					out[0] *= gain;
+					out[1] *= gain;
+					out += 2;
+					played_ += duration::from_frames(1);
+				}
+
+				return count;
+			}
+
+			std::size_t played() const override
+			{
+				return stream_->played();
+			}
+
+		private:
+			stream_ptr stream_;
+			EnvelopeFn envelope_fn_;
+			duration played_;
+			std::optional<std::size_t> remaining_;
+			std::optional<std::size_t> total_length_;
+		};
+
+	}
+
+	template <typename EnvelopeFn>
+	stream_ptr envelope(stream_ptr stream, EnvelopeFn envelope_fn, std::optional<duration> truncate = {})
+	{
+		return std::make_shared<envelope_impl<EnvelopeFn>>(std::move(stream), std::move(envelope_fn), truncate);
+	}
+}

libs/audio/source/effect/fade_in.cpp

@@ -1,71 +1,15 @@
-#include <psemek/audio/effect/fade_in.hpp>
+#include <psemek/audio/effect/fade_out.hpp>
-#include <psemek/audio/constants.hpp>
+#include <psemek/audio/effect/envelope.hpp>
-
+#include <psemek/math/interval.hpp>
-#include <algorithm>
 
 namespace psemek::audio
 {
 
-	namespace
-	{
-
-		struct fade_in_impl
-			: stream
-		{
-			fade_in_impl(stream_ptr stream, duration length, duration start)
-				: stream_(std::move(stream))
-				, length_(length)
-				, start_(start)
-			{}
-
-			std::optional<std::size_t> length() const override
-			{
-				return stream_->length();
-			}
-
-			std::size_t played() const override
-			{
-				return stream_->played();
-			}
-
-			std::size_t read(util::span<float> samples) override
-			{
-				auto const count = stream_->read(samples);
-				std::fill(samples.begin(), samples.begin() + std::min<std::size_t>(count, start_.samples()), 0.f);
-
-				if (count <= start_.samples())
-				{
-					start_ -= count;
-				}
-				else
-				{
-					for (std::size_t i = start_.samples(); i < count; i += 2)
-					{
-						float m = static_cast<float>(std::min<std::size_t>(current_, length_.samples())) / length_.samples();
-
-						samples[i + 0] *= m;
-						samples[i + 1] *= m;
-
-						current_ += 2;
-					}
-					start_ = duration{};
-				}
-
-				return count;
-			}
-
-		private:
-			stream_ptr stream_;
-			duration length_;
-			duration start_;
-			std::size_t current_ = 0;
-		};
-
-	}
-
 	stream_ptr fade_in(stream_ptr stream, duration length, duration start)
 	{
-		return std::make_shared<fade_in_impl>(std::move(stream), length, start);
+		return envelope(std::move(stream), [start, length](duration time){
+			return math::clamp(static_cast<float>(time.frames() - start.frames()) / length.frames(), {0.f, 1.f});
+		});
 	}
 
 }

libs/audio/source/effect/fade_out.cpp

@@ -1,75 +1,15 @@
 #include <psemek/audio/effect/fade_out.hpp>
-#include <psemek/audio/constants.hpp>
+#include <psemek/audio/effect/envelope.hpp>
-
+#include <psemek/math/interval.hpp>
-#include <algorithm>
 
 namespace psemek::audio
 {
 
-	namespace
-	{
-
-		struct fade_out_impl
-			: stream
-		{
-			fade_out_impl(stream_ptr stream, duration length, duration start)
-				: stream_(std::move(stream))
-				, length_(length)
-				, start_(start)
-				, total_length_(stream_->played() + start_.samples() + length_.samples())
-			{}
-
-			std::optional<std::size_t> length() const override
-			{
-				return total_length_;
-			}
-
-			std::size_t played() const override
-			{
-				return stream_->played();
-			}
-
-			std::size_t read(util::span<float> samples) override
-			{
-				if (current_ >= length_.samples())
-					return 0;
-
-				auto result = stream_->read(samples);
-
-				if (result <= start_.samples())
-				{
-					start_ -= duration::from_samples(result);
-				}
-				else
-				{
-					for (std::size_t i = start_.samples(); i < result; i += 2)
-					{
-						float m = static_cast<float>(length_.samples() - std::min<std::size_t>(current_, length_.samples())) / length_.samples();
-
-						samples[i + 0] *= m;
-						samples[i + 1] *= m;
-
-						current_ += 2;
-					}
-					start_ = {};
-				}
-
-				return result;
-			}
-
-		private:
-			stream_ptr stream_;
-			duration length_;
-			duration start_;
-			std::size_t current_ = 0;
-			std::size_t total_length_ = 0;
-		};
-
-	}
-
 	stream_ptr fade_out(stream_ptr stream, duration length, duration start)
 	{
-		return std::make_shared<fade_out_impl>(std::move(stream), length, start);
+		return envelope(std::move(stream), [start, length](duration time){
+			return math::clamp(static_cast<float>(length.frames() + start.frames() - time.frames()) / length.frames(), {0.f, 1.f});
+		}, start + length);
 	}
 
 }